Generally, optical displays are relatively large and complicated as evidenced, for example, by television and computer displays. Even when relatively small virtual display devices, such as disclosed in a copending patent application entitled "Compact Virtual Image Display", Ser. No. 07/767,179, filed Sep. 30, 1991, and assigned to the same assignee, are utilized, relatively high amounts of power are required. Generally this is caused by the fact that an incoherent image is produced and focused, by a plurality of lenses including the lens in the eye, onto the retina of the eye. Producing the incoherent image, whether it is real or virtual, requires substantial amounts of power and apparatus, which results in large and unwieldily structure.
In the prior art, a virtual image is produced by an array of light emitting diodes. The virtual image is then scanned by a mechanical mirror scanner with an image viewable by an operator being produced by imaging optics. This device is expensive, complicated to adjust and use, and is very sensitive to shock and other similar disturbances.
Direct retinal scanning devices have been devised, as for example the display disclosed in copending patent application entitled "Direct Retinal Scan Display", Ser. No. 07/857,193, filed Mar. 25, 1992, and assigned to the same assignee. In this device a scanning system is utilized in which light beams travel through the air and are scanned in a raster on the retina. Because of the distance travelled between the light source and the retina, relatively large scanning, or deflection, angles are required.